The Propeller Concept Applied to Free Flaps and the Proposal of a “Clock Flap” Nomenclature

Andrea Antonini1, Carlo Rossello2, Carlo Salomone1, Giuliana Carrega1, Lamberto Felli3, Giorgio Burastero1

1  MIOS, Infectious Diseases and Septic Orthopaedics, S. Maria di Misericordia Hospital, Albenga, ASL2 Savonese, Savona, Italy
2  Hand Surgery Unit, ASL2 Savonese, Savona, Italy
3  Orthopaedic Clinic, IRCCS, S. Martino Hospital, Genova, Italy


Background It is a common experience for reconstructive surgeons to feel the necessity for large flaps and minimal donor-site morbidity at the same time. In the reported cases where we felt this call intraoperatively, we have met our need by applying the “propeller concept” to fasciocutaneous or composite flaps, separating and rotating its different tissue components.

Methods We present a series of five cases in which we separated and rotated diversely fascial and cutaneous components of free perforator flaps to enhance the extension of the flap or to tailor it better on the tissue gap for optimal functional and aesthetic results. We also propose a simple nomenclature system for rotation angles’ definition, summarized as the “clock flap” classification, where the different components of the flap represent the arms of a clock which has the main vessel axis on the 12–6 line.

Results All reconstructive procedures succeeded with only minor complications. No partial failure due to vessel rotations was noticed.

Conclusion Applying “propeller style” rotations to different components of free flaps seems to be a safe procedure which may help maximize flap performance in terms of coverage of the recipient site, while minimizing scars and impairment of the donor site. Also, the proposed nomenclature gives the opportunity to record and compare surgical procedures for statistical analysis.


free flap – propeller – clock flap

The ideal free flap for soft tissue reconstructions should be reliable, potentially large in size, extremely adaptable to defect shape, and its harvest should cause as little donor-site morbidity as possible, both under a functional and aesthetic point of view.

Fasciocutaneous perforator flaps used as free tissue transfers are often smaller in size and much less moldable if compared with muscle flaps, especially if the aim is to achieve primary closure of the donor site. At the same time, the literature[1] [2] [3] [4] [5] [6] [7] and surgical experience on propeller flaps shows how these local flaps may be elevated both on a subfascial and suprafascial planes, with no significant difference on survival rates.

We therefore applied the “propeller concept” to our free flaps by splitting skin from deep tissues and rotating the tissues on the perforator axis, to meet the defect shape, size, and the need for movement in articular areas.

Materials and Methods

We report a series of five cases performed in our department from 2011 to 2014. In these procedures, the area to be covered turned to be larger and/or different in shape in respect to the fasciocutaneous paddles that had been harvested.

The patients were four males and one female, age range from 36 to 46 years. We therefore intraoperatively decided to improve the flaps’ congruity with the defects by applying the “propeller concept” to the flaps once they were revascularized in the recipient site.

In each case, different portions or components of the flap had to be diversely rotated on the vascular axes to obtain effective soft tissue reconstructions. Four flaps were fasciocutaneous anterolateral thigh (ALT) flaps, and one was an osteocutaneous fibula flap. They were all employed for delayed lower limb reconstructions after trauma and secondary infection.

We also propose a simple nomenclature for this technique which can be summarized as the “clock flap” procedure, where the vascular pedicle axis, or its tangent—if the pedicled is laid along a curved line, defines the 12–6 clock orientation, the deep tissue position is expressed as the hours’ arm value, while the superficial tissue axis will define the minutes in the clock’s time (see [Fig. 1]). The deep tissue may be bone muscle or fascia, while the superficial part will mainly be the skin paddle, but the classification can be applied to different kinds of composite flaps.

Fig. 1 Illustration of the clock flap concept, showing clock orientation on the main vessel axis, fascia rotation 30 degrees counterclockwise on the 5 hours’ position and skin paddle rotation 60 degrees clockwise on the 40 minutes’ position.

The deep tissue will be usually laid in the 6 hours’ position to minimize pedicle rotations, but in some cases, it may be necessary to apply some degrees of twisting to the deepest perforator segment as well. This nomenclature allows a 15-degree maximum approximation by considering only full hours and 5-minute intervals in clock arm movements.

In two of the five cases, we only needed to cover an area that was slightly larger than the fasciocutaneous island, and therefore, separated the skin from the fascia up to the perforator until we were able to safely rotate the skin paddle and the fascia from the vascular axis, as already described for the combined latissimus dorsi and thoracodorsal artery perforator flap or “razor flap”[8] and for the “gastrocnemius-propeller extended flap.”[9]

fig1Fig.1 Illustration of the clock flap concept, showing clock orientation on the main vessel axis, fascia rotation 30 degrees counterclockwise on the 5 hours’ position and skin paddle rotation 60 degrees clockwise on the 40 minutes’ position.


The deep tissue will be usually laid in the 6 hours’ position to minimize pedicle rotations, but in some cases, it may be necessary to apply some degrees of twisting to the deepest perforator segment as well. This nomenclature allows a 15-degree maximum approximation by considering only full hours and 5-minute intervals in clock arm movements.

In two of the five cases, we only needed to cover an area that was slightly larger than the fasciocutaneous island, and therefore, separated the skin from the fascia up to the perforator until we were able to safely rotate the skin paddle and the fascia from the vascular axis, as already described for the combined latissimus dorsi and thoracodorsal artery perforator flap or “razor flap”[8] and for the “gastrocnemius-propeller extended flap.”[9]

In these two straightforward cases, the “clock” flap rotations would be defined as follows:

  • A 30 × 10 cm fasciocutaneous ALT flap for a 20-cm ipsilateral fibulaprotibia transfer for acute posttraumatic osteomyelitis rotated in a 4:30 clock style ([Fig. 2]).

  • A 22 × 8 cm fasciocutaneous ALT flap for the coverage of an exposed patella and patellar tendon rotated in a 6:20 clock style ([Fig. 3]).

fig2Fig. 2 A 5:40 fasciocutaneous clock flap: the clock axis along the vessel in the anterior compartment (see text), the hours’ arm toward the grafted fascia on the 4 hours’ position, and the minutes’ arm along the vessels’ axis, therefore pointing 4:30. Notice the distal tip superficial necrosis.


fig3Fig. 3 (a) Knee wound after debridement and partial patellectomy for infected necrosis. (b) The ipsilateral ALT flap already revascularized on the medial genicular artery and its fascial and cutaneous components split on the superficial fascia layer up to the subcutaneous perforator. Fascia will need to cover the remaining patellar bone. (c) The skin paddle rotated on the perforator to cover the patellar tendon and allow knee flexion. (d) Donor site and flap fascia grafted with split-thickness skin grafts, and the application of the clock flap concept to the procedure. ALT, anterolateral thigh.

The reason for not keeping the vascular pedicle on the 6:00 axis in case 1 (as would seem the most logical option to minimize overall rotations) was that we preferred to lay the vessels deep inside the anterior compartment of the leg, where the anastomosis to the anterior tibial vessels was performed, to avoid vessel compression due to skin paddle and skin graft traction.

In both cases, the fascial component was covered with split-thickness skin grafts from the medial contralateral or ipsilateral thigh.

The other two ALT flaps were used for bilateral coverage of the ankle, and therefore, the fasciocutaneous paddle was split based on two different perforators, passing the distal one in the space between the Achilles’ tendon and the distal tibia. In one of these cases, after a terminolateral anastomosis of the lateral circumflex femoral artery (LCFA) to the posterior tibial artery in its middle third, the proximal paddle had to cover the medial face of the tibia (and a 7-cm resection of an infected fracture); therefore, the distal island was rotated of 180 degrees along the axis of the LCFA descending branch to reach the lateral submalleolar region and then approximately 60 degrees counterclockwise on the perforator axis to fit with its triangular shape the loss of substance, which can be summarized in a 6:20 clock style rotation of the distal skin paddle. The fascia corresponding to the distal skin paddle was kept on the 6:00 axis because its distal tip was used to reinforce the calcaneal insertion of the Achilles’ tendon; therefore, the cutaneous portion had to be rotated separately to fit the skin gap.

The other case was a separate coverage of both malleoli after an infected exposed bimalleolar fracture. In this case, after an end-to-end anastomosis to the anterior tibial artery, the skin was split into two different islands corresponding to two different perforators harvested, while the fascia was kept in continuity in between the two distinct perforators and tunneled in the space between the distal tibia and the Achilles’ tendon. The distal skin island was then rotated 60 degrees counterclockwise on a suprafascial plane to best fit the defect on the medial malleolus. The distal skin paddle was therefore also rotated in a 6:20 clock style.

The last case was a composite reconstruction of a posttraumatic infected loss of substance of the first metatarsal and dorsomedial soft tissues of the left midfoot. We harvested an osteocutaneous fibula flap from the right leg with an 18 cm × 6 cm skin paddle based on two different septal perforators. After an end-to-end anastomosis with the anterior tibial artery above the extensor retinaculum (level of traumatic vessel interruption) the 2.8-cm fibula segment was used to reconstruct the first metatarsal diaphysis along the same vascular axis. The skin paddle was unsuitable for size and orientation for direct closure of the entire soft tissue loss. It was, therefore, split into two islands based on the two different perforators. The proximal island received a 180-degree propeller rotation along the perforator axis to fill the soft tissue gap of the foot dorsum, while the distal island only needed a 90-degree rotation to cover the medial aspect of the midfoot ([Figs. 4] and [5]). It could be therefore summarized, being the bone the flap’s deep portion, as a “6:55, 6:15 double paddle osteocutaneous fibula clock flap.”

fig4Fig. 4 (a) Soft tissue necrosis overlying a first metatarsal bone gap after motorcycle trauma. (b) A harvested osteocutaneous fibula flap, showing the way in which it will be split into two different paddles based on the two perforators and corners marked with letters for better comprehension (distal tip excised). (c) Flap after insetting. The two islands have been rotated to fill the soft tissue gap in the best possible way. A–G mark the corners of the two skin paddles.

fig5Fig. 5 The final result of the case 1 year after the procedure. (a) Final donor site and reconstructed foot appearance with no secondary surgery. (b) X-rays showing the underlying effective bone reconstruction, preserving the metatarsal formula and foot morphology.

All splittings and rotations were performed after flap revascularization, positive patency tests, and evaluation of physiological perfusion of the entire skin paddle.


All microvascular flaps survived. In one case (the split ALT flap for bimalleolar coverage), we had an early postoperative venous congestion with a thrombosis due to kinking of the main pedicle vein, just distal to the site of anastomosis, in the pedicle segment proximal to any rotation site, and therefore, not attributable to the vessel rotations. Anastomosis was revised and thrombus removed within 20 hours from the primary procedure with complete flap salvage.

In another case (the 4:30 ALT clock flap), we had a superficial necrosis of the distal tip (2.5 cm) of the 30-cm long skin paddle ([Fig. 2]), without any exposure of deep structures, and complete secondary healing with no need for further surgical treatment. This minor complication might be due to the separation of the two components of the flaps, and we admit that maintaining the fasciocutaneous connections between the plexuses could have improved the skin survival, but we also know that 30 cm is about the maximum allowed length for an ALT flap harvested on a single proximal perforator.

All other flaps had uneventful postoperative healing. Three ALT flap donor sites out of four were closed primarily ([Fig. 6]), the ipsilateral ALT for knee coverage donor site was grafted to avoid skin traction proximally to the anastomotic site which could affect venous hemodynamics, but eventually all grafted areas were excised concomitantly to a femoral nail removal 8 months after the primary procedure ([Fig. 7a]). The fibula donor site was grafted ([Fig. 5a]).

fig6Fig. 6 The donor site of the largest ALT flap described in this article (30 × 10 cm), 3 months after primary closure. ALT, anterolateral thigh.


fig7Fig. 7 The final result of case in [Fig. 3]. (a) Result 5 months postoperatively with skin grafts on donor site and on fascial component of the flap. (b) Good knee ROM thanks to flap enhancement applying the “clock flap” technique. (c) Final result after the excision of grafted areas 8 months after the flap procedure, while removing a femoral nail. ROM, range of motion.


Skin grafts on fascial components had normal healing behavior (revascularization by neoangiogenesis visible after 6 days, 70–95% survival rates, and complete re-epithelialization of grafted area in 3–5 weeks).


This technique gave us the possibility to enhance the area a harvested flap could cover or helping our skin paddles fit the defects without traction, excessive bulkiness or unaesthetic wrinkles due to incongruence between flap and recipient site margins, without jeopardizing flap vitality nor needing to add donor-site scarring.

Of the two minor complications reported, only one (the superficial necrosis of the distal tip of the skin paddle) could be in relation to the surgical technique proposed, on the basis of a physiopathological reasoning. In our experience, though, superficial skin necrosis on the tip of a 30-cm long ALT flap with a single proximal perforator is a possible complication for the “traditional” fasciocutaneous flap as well.

This technique, hereby described as an intraoperative means to enhance a flap’s covering potential, is in our opinion to be kept in mind for cases where final debridement leads to a tissue gap larger than expected, or when the skin paddle shape does not perfectly fit the loss of substance, as for the cases described in this article.

Of course, it may also be implemented as a preoperative decision, but in this case, it will have to be evaluated in comparison with other techniques.

Preexpansion of skin flaps, for example, may be a good solution to cover large defects or to be tailored to fit a peculiar shape, but it is not always compatible with reconstructive timing necessities, especially when dealing with trauma and infection as in our everyday practice. An alternative to the clock flap technique, of course, is the use of larger flaps, tailored, and customized to the defect, such as the deep inferior epigastric artery perforator flap,[10] which can provide a large amount of cutaneous tissue with a very acceptable scar.

The kiss flap technique[11] is, instead, the most direct competitor to the clock flap procedure, since it may be planned intraoperatively as well as before the procedure. Advantages of the clock flap technique are the dissection of one single pedicle (instead of multiple pedicles for the different “kissing” flaps) and the possibility to have one single donor site and linear scar. Disadvantages, instead, are the frequent need for skin grafting over fascial or muscle components (and the related graft donor-site morbidity), as well as the necessity of a more meticulous, careful and dangerous dissection of the pedicle inside the flap area which probably requires a more experienced and confident microsurgeon.

Our technique is yet one more option for surgeons coping with irregular or large soft tissue defects because it offers the opportunity to enhance the fasciocutaneous flap’s reach for large areas reducing the need for larger flaps and allows to mold the skin and fascia paddles to the best possible shape, leading to a better functional and aesthetic result of both donor and recipient sites.

Our proposal for a new nomenclature aims to offer surgeons and scientists the possibility to evaluate success rates and compare complications on the basis of rotation angles of the free flaps’ components. We believe the application of the clock arms’ parallelism to flap paddle components may be a synthetic and easily understandable way to define the operative technique which may be useful to colleagues having to cope with early microvascular complications in such complex procedures, as well as to surgeons trying to classify their flaps for statistical analysis, as many authors are already doing with pedicled propeller flap case series, trying to formulate standard rules to minimize vascular complications.[7] [12] [13] [14] [15] [16]


In our opinion, based on the small experience reported, perforator flaps may be considered structurally the same, no matter whether they are used as local flaps or they are transferred as free flaps. This means they can be split according to angiosomes of the donor site into different islands based on different perforators, and even separated into fascial and cutaneous components based on a single perforator, relying on the different plexuses (dermal/fascial) that perfuse the two different layers.

Of course, more cases and better experience are mandatory to validate the hereby proposed technique.


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Address for correspondence

Andrea Antonini, MD, MIOS
Infectious Diseases and Septic Orthopaedics, S. Maria di Misericordia Hospital
Ospedale SMdM, via martiri della Foce, 40, 17131, Albenga, Savona


Thieme Journal of Reconstructive Microsurgery